Bolaget svenska ktrtlagekpabbiken



A. e. amuusa'su. METHOD OF HEAT TREATMENT AND FURNACE THEREWR.

APPLICATION FILED I M. l4. NH?- 1,401,983.- Patented Jan. 3, 1922.

3 SHEETS-SHEET ]NVENTOR By "Attorneys, awn, 0M4 M A. G. E. I IULTGREN. METHOD OF' HEAT TREATMENT AND FURNACE THEREFOR. Armcmon FILED an. n, ma.

1,401,983. Patented Jan. 3, 1922.

3 SHEETFSHEET 2- Fi Z.

A. G. E. HULTGBEN. METHOD OF HEAT TREATMENT AND FURNACE THEREFOR. APPLICATION FILED rm. :4, ms.

1,401,983, Patented Jan. 3,1922.

3 SIIEETHIIEET 3.

INVENTOR a By Attorneys, i?

UNITED STATES PATENT OFFICE.

AXE]; GUST-AI EMANUEL HULTGREN, OF GOMENBOBG, SWEDEN, ABSIG-NQB BOLAGET BVENSIA. KULLAGERFABBIKEN, OF GOTTENBOBG, SWEDEN,

MION 0F SWEDEN.

METHOD OF HEAT TREATMENT AND FURNACE THfiBEEOR.

Specification 01' Letters Patent.

application filed March 14, 1919. Serial No. 282,717.

To all whom it may concern:

Be it known that I, Axon Gusrar EMAN- unn Homoneu, a subject of the Kin of Sweden, residin at Gottenborg, in the I ngdom of Swedcmliave invented new and useful Improvements in Methods of Heat Treatment and Furnaces Therefor, (for which I filed an up licution in Sweden on Mar. 4, 1918,) of which the following is a specification.

This invention relates to the heat treatment of rotatable bodies, and to furnaces therefor, particularly for heating bearing rings and washers for [call and roller bearings or blanks adapted to such rings and washers, or other symmetrical objects of circulur outline, which are generically of the character of solids of revolution.

An ob'ect of the invention is to effect a uniform heating of such objects for hardening, forging, annealing, tempering, or other treatment with heat.

Another object is to bring about an automatic operation and an economical utilization of the heat supplied.

These objects are very desirable when treating bodies of the above kind with heat. Uniform heating is of rent importance for the quality of the proc uct and at the same time diflicult to effect owing to the shape of said objects, which have u. great extension in relation to the mass. Automatic work and rational utilization of the fuel are important factois, especially when such objects are manufactured on a great scale.

On examining critically the known is pes of furnaces for similar purposes, it wi be found that the above deslderatn are not realized simultaneously in one and the same tv )e.

lVith reference thereto the non-automatic furnaces may immediately be left out of consideration, since in such furnaces no rational utilization of the escaping combustion gases for preheating the cold material takes place. 0

For effecting automatic operation various methods have been used, and the most important ones of such methods will be mentioned in the following.

In case of heating furnaces for small objects of round or square form, as rivets or the like, it has been suggested for said purpose to incline the bottom of the furnace, the

objects thereby being caused to move through the furnace by their own weight. In this case it has not been aimed at to adjust the inclination of the bottom of the furnace in such manner that a rolling movement is affected, 11': order to obtain uniform heating of the objects, since no necessity therefor has been present, substantially on account of the small dimensions of the objects.

It has also been proposed by means of mechanisms operating in the furnace to cause the bodies to pass through the furnace, thus bringing about an automatic 0 eration of the same. Such furnaces are, owever, of no use in the present case, since mechanisms operating at high temperature will very soon be destroyed, and, besides, are rather complicated. Furthermore, uniform hcati of all parts of the objects cannot be obtained in such furnaces, especially in those having an extended furnace chamber, it bein practically impossible to efl'ect an even distribution of bent, since the ortion of the chamber near the roof of the l'urnace will be hotter than the portion near the bottom or vice versa.

.The only way to give the objects uniform teu'lperuture during automatic feeding in a furnace the different parts of which have unequal temperature, is to effect the feeding movement, white causing the bodies to ro tute at the same time.

Such a method proposed in connection with annealing furnaces consists in introducing the objects to be heated into cylindrical receptacles and causing the feed of the receptacles to take place on account of their own weight, while rolling down an incliucd bottom of the furnace. This method is, however, connected with the serious inconvenience that the receptacles originally of cylindrical form will be deformed because of t e influence of the heat and the load, the rolling movement thereby being prevented. In this connection it is to be noted that even small deformations are of rent importance. Besides, this method is use as if the heated objects arc to be subjected instantly to further treatment, as for instance hardening forging or the like, because the emptying of the receptacles in heat is connected with waste of time, coolin of the material and other inconveniences. 7

According to the present invention which Patented Jan; 3, 1922.

reiates only to heating of bearing rings and washers for ball and roller hearings or blanks adapted to such rings and washers, and similar circular objects the above-mentioned inconveniences are avoided by the objects themselves being fed through the furnace chamber by their own weight, while rolling continuously or intermittently along the bottom of the, furnace which, for this purpose, possesses an exactly adjusted inclination.

The conditions to be fulfilled, in order that in such a. furnace a rollin movement of all the work pieces shall rea y take place, will appear from the following explanation.

. Supposing in the first instance that a single ring is standin on a plane inclinedsu port having an ang e of inclined a, it will e easily seen that, in case the support has an insuflicient inclination, the ring, owing to the frictional contact therewith, assumes a position of uilibrium; no movement will take place. irst at a certain angle of inclinaticn the ring will commence to move, that is to so. to roll. This angle is termed the angle 0 rolling friction and is denoted in the following by V The angle depends among other things on the following factors, viz. the material, the uality of the surface and the temperature 0 the sup port and of the ring as well as the weight and the size of the ring.

Ii agvmh. the ring must be actuated by a counteractin force in order to be prevented from moving. If this force be removcd, the rin begins t move down the plane, while rolling. Pure rolling will, however, take place only in case of a falling below a certain value: V H agv the movement will take place in such manner that the ring is rolling and at the same time sliding on the support. This depends on the fact that the pressure against the support is so slip-ht that the friction caused thereby is in icient to prevent s iding. To this effect contributes also the circumstance that the component of the gravity acting in the. direction of the movement is rather considerable. Summarizing the above, it will be seen that the condition of a single body havin the shape of a solid of revolution and place: on an inclined plane beginning to move by itself, while rolling, is that mln mer In the following the circumstances prevailin if several rings placed in a row, one hchinc another, are to be fed forward, will be investigated. Here three different events are to be distinguished:

In this case a forward feed will take place only in case a power of sufficient magnitude pushin from behind be present. Otherwise, the bodies will be at rest. On investigating the conditions of each separate ring in-a row, it will be seen that the foremost ring for movin has to be pressed from behind by the secon ring, which is counteracted by an equal reaction pressure exerted by the first ring and, owing thereto, has to be actuated by a still greater pressure exerted by the third ring for beginning to move and so on. In other words, if any movement should be effected, the sftermost rin is to be actuated by a pressure equalling the sum of the re slstances of all the rings to the movement. Between two adjacent rings there is acting a pressure which is the greater, the nearer the inlet end the ring is positioned and the less is the inclination.

In order that any rin for instance the n :th rin in a row, counte from the forward end, shall roll durino the forward movement, it has to maintain t e engagement with the support, while sliding in relation to the adjacent rings, that is to say, the frictional power in the point touching the support has to be greater than the sum of the frictional powers in the points touching the two rings. The latter frictional powers are proportional to the ressures actlng between the rings, and, OWlllg thereto, are the greater, the more the rin v is positioned at the back of the row, while t e former frictional power caused by the component of the gravity forming right angles with the sup ort of each ring of the row cannot exceed tic value f.Pcos a, f being the corresponding coefficient of friction and P the weight of the ring. It will there fore be evident that, concernin a certain ring of the row, as for instance e n :th ring from the forward end, the frictions against the support and the two adjacent rings may balance each other, and, consequently, no roiling movement can take place. As for all the preceding rings, the feed will take place by a rolling movement, while the succeeding rings will be fed by a slidin movement on the support. Obviously, t circumstance will be apparent, if a reaches its minimum, that is to say, if the sup ort is horizontal. By experiments made not I hearing rings of ball bearings in heat on a horizontal support n in this case was found to be 2 3 to 4. If a increases, n will be greater.

In this case the feed will take place automatically. If the feed is to be controlled a power actuating the foremost ring and irected backwards must be exerted. The aftermost ring exerts, owino to its weight a pressure against the preceding ring which in turn actuates the next ring by a pressure twice as large and so on. The result of this will be that the conditions of pressure and friction between the rings will vary throughout the row in reversed order relatively to most rings equal to t the event 1. Therefore, if the first ring he allowed to passihill the rings will be fed forward, the n a most rings, while rollin%-, and the remaining foremost rings, while slir ing. If'a decreases, as will be increased.

From the above it may be evident that in case a=V n= that is to say, for this inclination, min, an infinite number of rings may, theoreticall taken be fed forward, one after another, while rolling on account of a ushing power 0. Since in reality little differences in the frictional circumstances are unavoidable in the difi'erent rin said proposition may be changed to the 0 lowing one valid in practice: if a=V a slight power pushing from behind will cause all the nu of the row to be fed forward while mlifig.

If 0: increases or decreases from V there will be a risk of art of the rims in the row slidin in the ormer case the orewi slide, and in the latter case the aftermost rings. his risk is the greater, the greater is the number of rings.

Consequently, the condition of all the solids of revolution arran ed in the manner described rolling, wh' e fed forward, through a furnace of the type mentioned above is as follows:

The support our ing the work pieces should have an inc ination equal or approximately equal to the angle of rolling friction under the provailin circumstances.

e lesser is the number 0 work pieces 111 one and the ame row, the greater may he said angle to the horizontal, but said angle may not exceed a certain value at which, concerning a rin in the row where the pressures exerted by adjacent rings are the greatest (said pressures bemg caused either by the weight of the rings or by the feeding pressure), the sum of the torques of the frictional owers caused by said pressures is he torques of the friction against the support.

This invention provides a method of heat treatment and a furnace therefor wherein the bottom or hearth of the elongated and nearl horizontal furnace chamber through whic the rings or other objects roll in series, has a slope which accords with the conditions hereinbefore stated, ivith controllable means for heating the chamber to the required temperature, and means for determining or controlling the rate of progression of the rolling ob'ects through the furnace. The invention u-ther comprises other features of method and apparatus, as will be defined in the claims. 1e heating devices are placed in correspondence to the use ofthe furnace. They are enerally locatcd along a part only of tie chamber, counted from the outlet end. In annealrided with gas burners 3 in% furnaces they may be placed along the m1 dle portion of the chamber, no heat' devices being provided at the outlet In all cases the inlet end is heated by the escapin gases of combustion only. The inclination of the bottom is equal or approximately equal to the angle of rollin friction under the circumstances, prevai ing. By this it isuttained that the rings or washers introduced at the higher end of the chamber pass throu h it owing to their own weight, while ro ing intermittently or continuously, thus being heated uniformly. The speed is so controlled that the rings, when passin through the furnace, receive in a suitab e place such maximum temperature or are sub ected to such heating or cooling as is intended by the heating process in question.

The control of the progress of the rings or objects throu h the furnace chamber is best accomplishe by introducing checking or retarding means at or near the discharge end, such means being adapted to passivel or actively stop or retard the rings at suc l end, with provision for discharging the rings one by one at suitably timed intervals.

Preferably intermittentlyacting releasing or discharging means are provided at the outlet end, and intermittently-acting feeding means at the inlet end, these respective means being driven from the same source and at the some effective rate of speed, so that for each ring discharged at the outlet, a new ringis introduced at the inlet, thereby kee ing the furnace chamber always filled wit rings undergoing treatment.

A preferred embodiment of a hardening furnace constructed according to the invention is illustrated in the accompanying drawn]? in whichis a side view and partiall a longituc 1nal section of the furnace. "g. 2 is a plan view and partially a horizontal section thereof. Fig. 3 is a cross-section on line A--B in Fig. 1. Fig. 4 is a section cor responding to that shown in Fig. 3 and illustrating a somewhat modified form of the bottom of the furnace.

Referring to the drawings, the furnace consists of an extended channel 1 made'of brick-work, the foremost portion of which situated next to the outlet 0 ening 2 is proor heating the channel to the tem erature desired. Disposed in the channe is an inner bottom 4 provided with longitudinal recesses or grooves 5 guiding the rings 6 to be heated and having an inclination so adjusted in the manner mentioned above that the rings placed in said grooves are caused to roll through the furnace by their own weight. Preferably, the said bottom 4 is freely accessible in the interior of the channel so as forth in detail to be capable of being cuwmpped by the flames of the gas burners at the'sidcs us well a at the foremost end. The supply of heat at the said end is controlled by means of valves or dampers 7, adjustable up or down by screws, one for each groove 5 in the not; tom 4, and positioned at the lower, foremost portion of the channel. The introduction of the rings 6 taking place at the back of the furnace is preferably efiected automatically by means of rotating arms 8 catching; the rings 6 which 5!.1'8 placed in a suitably inclined magazine 9, said arms causing them to mount a sloping truck 10 from which they drop in such a manner as to remain stunding on the edgein the roores leading to the furnace. This feeding uppnrehis is r It in my application filed August 10, 1918, Serial N 0. 249.366. The present invention i not limited to this or to soy specific feeding-in mechanism. By the use of a. feeding device of this kind it is ettained, in conjunction with a reliable and continuous supply of rings to the furnace, that the rings dropping from the sloping track push, when entering; the iurncce, the sftermost ring in each row, said action being propagated through all the rir s in the row, thus preventing interruptio .s or dis turbnnces of the accurate feed of the rings in the furnace caused for instance by smal particles entering the furnace or disengaged from its walls The rate of feed is (Til itrolled by meuns provided at the for 0st or discharge end of the furnace and. grez-F- orably, acting to advance the rings in... ms-

tently, that shown consisting of stop rods or slides 11, 12 supported by arms 14 which are actuated by means or" com disks 15 secured to u rotating shaft 16 o as to raise the stops 11 and 12 ultcinetingly. As the stop 11 is raised, the foremost ring in the row will be released so as to be cnpublc of droppim through the chute 1.7 into the hardening b ot-h 18, while the stop 12 blocks the remaining rings. The stop 11 is then dropped and the stop 12 raised, which releases the end ring and allows it to roll freely down until stopped by the stop 11, this movement being propagated successively through all the rings behind. so that the frictional traction between them is successively released, and all the rings in tl row roll forward one step or space. The 1 of feed is so controlled that the rings are hected to the temperature desired, before being 'let out of the furnace.

The combustion formed in the foremost art of the furnace and passing throng the same in opposite direction to the rings, transfer successively the heat to the latter. By this a. rational utilization of the heat supplied is obtained.

The described mechanism contributes in on important sense to this result by insuring that the ring shall roll forward at each movement a distance equal to their dimneter, whereby each ring turns a. scant third of a revolution (3.1416+3) at each movement, so that in each stopping position a new portion of the ring rests agamst the heated hearth and the rim is newly positioned to the hot gases circ sting above; and so that after each third feed the rin has performed less than one complete revomtion, with the reult that the successive points of contact with the hearth are never the same, but instead pror ress circumferenticlly around the individual rings, thus insuring in a most perfect manner the uniform and symmetrion] heating or heat treatment of the rings, so that each ring may receive the some treatment around its entire circumference as the result of its passuge through the furnace.

The chute 17, being preferably in close conjunction with the outlet end 2 of the furnace and so inclined and shaped that in this chute also the rings 6 are caused to roll, is closed at all sides and extends below the surface of the hardening both 18 thus forming a liquid seal which prevents cold air from entering the furnace at the outlet end. i u rthermore, at said end an inssection openinn havinga door 19 is provi ed, through which, if desired or required, the foremost rings in each row are accessible from the outside also.

In 4 a somewhat modified form of the bottom 4 of the furnace as illustrated. This form diflers from that shown in F ig. 1 chiefly in that one side wall and the bottom of each groove 5 are inclined in lateral direction thereby musing the rings 6 to assume an oblique position in which they are guided by the inclined side wall and the bottom. This embodiment aifords the advantage that rings having different widths may be placed 1n the groove 5', without changing the Width of the groove. Furthermore, in such grooves rings or washers may be guided the periphery of which is formed according to any other surface of revolution than the cylindrical surface shown, as for instance :1 conical exterior, or on exterior which is non-equatorial spherical zone, as is the case with the supporting rings of certain self-adjusting axial ballbearings.

The furnace is not limited to heating with gas but may, of course, be heated by any other kind of fuel, as for instance oil or ascertained the -freed from restraint by the one solid fuel. Nor is the freely disposed bottom of the furnace shown in the drawings indispensable, smce the furnace chamber mag consist of a single channel.

avlng now particularly described and nature of my said invention and in What manner the same is to be performed, I declare that what I claim is l. The method of heat treatment of s metrical circular objects constituting solids of revolution, which consists in passing them in a continuous succession through a long chamber in which they are directly exposed, the bottom of which chamber has such inclination that the ob'ects advance with a rolling traction on the ttom while sliding against one another at their points of tangential contact. simultaneously heating such chamber, and controlling the progress of the objects through the chamber at such rate with reference to their mass and to the temperature and length of the chamber as to subject each of the successive objects duri its rolling progression to the prescrib dfi heat treatment.

2. The method of claim 1, the control of the'progress of the objects being accomplished intermittently at the discharge end of the chamber by the successive release of the terminal objects and, whereby as each ob'ect is released it is free to roll forward inc ependently of those behind it, which follow in succession, so that as each object is ahead, it tends by starting forward to reduce the restraining engagement with those behind.

furnace for heat treatment of rings or analogous s mmetrical circular objects constituting so ids of revolution, comprising an elongated furnace chamber adapted to hold a considerable series of such ohjects in serial contact and exposed directly within said chamber having means for loterally engaging and guiding the objects during their rolling progress to hold them substantially upright, and, said chamber havi a sloping bottom of such inclination that t e circular objects advance by gravity with a rolling traction on the bottom while sliding against one another at their points of tangential contact, with means for admitting said objects at the higher end, an outlet at the lower end, means for controlling the rate of regress of such objects through said chem er, and means for heating said chamber and for controlling the temperature thereof, whereby to determine the duration and extent of the heat treatment of the objects therein,

4. A furnace according to claim 3, havmg intermittent means for controlling the progress of the objects acting u on the ob ects at the outlet end of the chum er. said means adapted to release and arrest the terminal object and afterward to release the next following object, whereby to feed forward theentire series one space.

5. A furnace having an elongated heatin chamber with a slo nng bottom and longitudinal lateral gui g means, adapted to hold a series of rings or analogous objects and cause them to program through it by rolling in an upright position by force of gravity, and intermittent feeding mechanism at the outlet end includin two alternately acting stops, the one a opted to hold and release the terminal ring, and the other to hold and release the next ring in series whereby the remaining rings of the series are held by engagement each with the preceding one.

6. A furnace according to claim 5, the stops movable out of and into the path of the rings, and rotative means for so mov ing them alternately.

7. A furnace according to claim 5, the stops consisting of rods entering the furnace chamber, levers carrying the rods, and a rotary cam moving said levers alternately.

8. A furnace acoordin to claim 3, having means for successively ischarging the objects from the outlet of the chamber, means for successively feeding in the objects at the inlet end, and driving means impelling both said means at equal effective eds.

9. A furnace according to claim 3, the a'uiding means being a channel in the furnace bottom adapted to laterally engage the objects as they progressively roll through the chamber.

10. A furnace according to claim 3, having a bottom or hearth over which the ob jects roll, with a combustion chamber beneath such bottom, with means for affording communication for combustion gases at the sides of said bottom, whereby hot gases may flow from beneath the furnace bottom to the chamber above.

11. A furnace according to claim 3, having a bottom or hearth over which the objects under treatment roll, with a combustion chamber beneath said bottom, said hearth having multiple channels for guiding the objects as they roll through the chamber in a. plurality of series, burners introducing combustible to said lower chamber. and dampers for controlling communication with each chamber near the discharge heat to the work pieces, and grooves in said veiling and adapted to cause the workupper bottom adapted to guide the workpieces to roll through the furnace by their pieces, each of said 'rooves having sideown weight and to be heated to the temper- 10 walls and bottom inclined in lateral direcature desired.

tion, the upper bottom having an inclina- In testimony whereof I have signed my tion about corresgonding to the angle of name. rolling friction un er the circumstances pre- AXEL GUSTAF M U HUI-TGREN. 

